admin
47dd0bd244
internal/escrow: zero-knowledge escrow creation. R = 10 EFF-wordlist words (crypto/rand, ~129 bits); wrap K under R via PBS-native key change-passphrase driven over a stdlib pty (x/sys/unix; output discarded so R can't leak, F-A2); self-verify the blob recovers K (fingerprint match) before shipping. Opt-in (b) R-wrapped offline copy + (a) raw paperkey. Live K is byte-unchanged (operates on a copy). --selftest=escrow-create (-storage/-paperkey/-offline/-upload). Posture config field (zero_knowledge default). PBSEncKeyPath helper. Grounded by the escrow spike findings. Tests: R entropy>=128/format/uniqueness; integration round-trip (wrap->unwrap fingerprint match, wrong-R fails, K byte-unchanged) guarded to linux+pbc. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
57 lines
2.0 KiB
Go
57 lines
2.0 KiB
Go
//go:build linux
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package escrow
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import (
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"context"
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"fmt"
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"io"
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"os"
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"os/exec"
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"strings"
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"syscall"
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"golang.org/x/sys/unix"
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)
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// runWithPassphrase runs a TTY-requiring command (PBS `key change-passphrase`, F-A1 in the spike
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// findings) on a pty, feeding `passphrase` `reps` times (once per prompt) and DISCARDING all pty
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// output so the echoed passphrase can never leak (F-A2). Linux-only — the agent runs on Proxmox
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// hosts; a non-linux stub returns an error.
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func runWithPassphrase(ctx context.Context, passphrase string, reps int, name string, args ...string) error {
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master, err := os.OpenFile("/dev/ptmx", os.O_RDWR, 0)
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if err != nil {
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return fmt.Errorf("escrow: open ptmx: %w", err)
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}
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defer master.Close()
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if err := unix.IoctlSetPointerInt(int(master.Fd()), unix.TIOCSPTLCK, 0); err != nil { // unlock
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return fmt.Errorf("escrow: unlock pty: %w", err)
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}
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ptn, err := unix.IoctlGetInt(int(master.Fd()), unix.TIOCGPTN)
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if err != nil {
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return fmt.Errorf("escrow: pty number: %w", err)
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}
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slave, err := os.OpenFile(fmt.Sprintf("/dev/pts/%d", ptn), os.O_RDWR|syscall.O_NOCTTY, 0)
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if err != nil {
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return fmt.Errorf("escrow: open pts: %w", err)
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}
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defer slave.Close()
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cmd := exec.CommandContext(ctx, name, args...)
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cmd.Stdin, cmd.Stdout, cmd.Stderr = slave, slave, slave
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// New session + the slave (fd 0) becomes the controlling terminal, so the child's tty prompts
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// read from / write to the pty rather than failing "no tty".
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cmd.SysProcAttr = &syscall.SysProcAttr{Setsid: true, Setctty: true}
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if err := cmd.Start(); err != nil {
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return fmt.Errorf("escrow: start %s: %w", name, err)
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}
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// Feed the passphrase once (the tty line discipline buffers both lines for the sequential
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// New/Verify prompts), then DISCARD everything the pty emits — the passphrase is echoed back
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// on the master fd and must never reach a log.
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go func() { _, _ = master.WriteString(strings.Repeat(passphrase+"\n", reps)) }()
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go func() { _, _ = io.Copy(io.Discard, master) }()
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return cmd.Wait()
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}
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